Niger's parliament has unanimously approved the deployment of troops to northern Nigeria as part of a regional offensive against Islamist militant group Boko Haram, which has launched several cross-border attacks in recent days.

Nigeria, Niger, Cameroon, Chad and Benin agreed at the weekend to send a joint force of 8,700 troops to battle the militant group, which has killed thousands of people and kidnapped hundreds more in its bid to carve out a caliphate.

The crisis has prompted Nigeria to postpone its Feb. 14 presidential election by six weeks.

In recent days, Niger has massed more than 3,000 troops in its southern region of Diffa on the border with Nigeria, awaiting parliamentary approval to go on the offensive.

"The pooling of the efforts and resources of concerned countries will contribute without doubt to crushing this group which shows scorn, through its barbaric acts, for the Muslim religion," Niger's parliamentary speaker Adamou Salifou said after the vote late on Monday.

"Our country has never failed it its solidarity with its neighbors," he said.

The vote was supported by all 102 deputies present.

On Monday, Boko Haram militants bombed the Niger town of Diffa, killing five people - its third attack there in four days. It also carried out raids in neighboring Cameroon, kidnapping a bus full of passengers.

Residents in Diffa have voiced fears of further attacks in the coming days. Locals in the town, which lies just a few kilometers from territory controlled by Boko Haram, have long spoken of sleeper cells infiltrating their communities.

An intensification of Boko Haram violence near Lake Chad, which straddles Nigeria, Chad,Cameroon and Niger, has sent tens of thousands of Nigerians fleeing across the border.